Vibration dampening of a power tool

ABSTRACT

The invention provides a power tool assembly having a motor. The power tool assembly includes a housing having an inner surface defining a cavity enclosing the motor. The power tool assembly also includes a layer of polyurethane elastomer disposed on the inner surface and extending into the cavity. The polyurethane elastomer dampens vibration of the motor during operation of the power tool assembly.

FIELD OF THE INVENTION

The invention relates to dampening vibration associated with a power tool.

BACKGROUND OF THE INVENTION

Power tools often generate vibration that can be transferred the operator's hand when the tool is grasped and used. The vibration can be unhealthy to the operator. For example, the operator's wrist and fingers can be strained and can create a condition known as a white finger effect. Another problem associated with the vibration of a power tool is that vibration makes it difficult to keep the tool in a precise position. This can result in damaged work-pieces and can expose the operator to injuries due to recoil and misdirected blows.

Accordingly, it would be desirable to develop a material, for example, for dampening vibration in a power tool while not increasing the operating temperatures of the tool or interfering with the operation of the tool

SUMMARY OF THE INVENTION

The subject invention includes a power tool assembly having a housing with an inner surface defining a cavity. A motor is disposed within the cavity of the housing and coupled to the inner surface. A layer of polyurethane elastomer is disposed at least partially on the inner surface for dampening vibration of the motor during operation of the power tool assembly. The subject invention also includes a method of assembling the power tool assembly. The method comprises the steps of: disposing the layer of polyurethane elastomer on the inner surface and enclosing the motor within the inner surface of the housing wherein the layer of polyurethane elastomer dampens vibration generated by the motor during operation of the power tool assembly.

Accordingly, the subject invention incorporates a layer of polyurethane elastomer into the power tool for dampening vibration of the power tool. The polyurethane elastomer, however, does not contribute to increasing the operating temperatures of the tool and does not interfere with the operation of the tool.

BRIEF DESCRIPTION OF THE DRAWINGS

Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

FIG. 1 is an exploded view of a power tool according to a first exemplary embodiment of the invention;

FIG. 2 is an exploded view of a power tool according to a second exemplary embodiment of the invention; and

FIG. 3 is an exploded view of a power tool according to a third exemplary embodiment of the invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A plurality of different embodiments of the invention are shown in the Figures of the application. Similar features are shown in the various embodiments of the invention. Similar features have been numbered with a common reference numeral and have been differentiated by an alphabetic designation. Also, to enhance consistency, features in any particular drawing share the same alphabetic designation even if the feature is shown in less than all embodiments. Similar features are structured similarly, operate similarly, and/or have the same function unless otherwise indicated by the drawings or this specification. Furthermore, particular features of one embodiment can replace corresponding features in another embodiment unless otherwise indicated by the drawings or this specification.

Referring now to FIG. 1, in a first exemplary embodiment of the invention, a power tool assembly 10 includes a motor 12. The first exemplary power tool assembly 10 is a hammer drill. The power tool assembly 10 also includes a housing 14 having an inner surface 16 defining a cavity with the motor 12 disposed within the cavity and coupled to the inner surface 16. The power tool assembly 10 also includes a layer of polyurethane elastomer 18 disposed at least partially on the inner surface 16. In the embodiment of FIG. 1 the layer of polyurethane elastomer 18 covers substantially all of the inner surface 16 of the housing 14. The polyurethane elastomer 18 dampens vibration of the motor 12 during operation of the power tool assembly 10.

The layer of polyurethane elastomer 18 can be engaged with the inner surface 16 by different methods. In a first exemplary method for assembling the power tool assembly 10, the layer of polyurethane elastomer 18 can be disposed on inner surface 16 by adhering the layer of polyurethane elastomer 18 to the inner surface 16 with an adhesive. The layers of polyurethane elastomer 18 can be cut from sheets of material into any suitable configuration. Alternatively, the layer of polyurethane elastomeric 18 may be secured to the inner surface 16 by any suitable mechanical interlocking feature. In another exemplary method for assembling the power tool assembly 10, the layer of polyurethane elastomer 18 can be disposed on inner surface 16 by overmolding the layer of polyurethane elastomer 18 on the inner surface 16. As should be appreciated, the layer of polyurethane elastomer 18 can be secured to the inner surface 16 by any suitable method so long as the transmission of vibration to the layer of polyurethane elastomer 18 is not impeded.

The first exemplary power tool assembly 10 includes a tool member 20 coupled to the motor 12 and driven in motion by the motor 12. The first exemplary tool member 20 is a drill bit chuck.

The housing 14 preferably includes a first housing shell 22 defining a first portion 24 of the inner surface 16. The housing 14 also includes a second housing shell 26 defining a second portion 28 of the inner surface 16 with the second housing shell 26 being connectable to the first housing shell 22 to define the cavity. A plurality of first bosses 30, 32, 34, 36, 38, 40, 42, 44 project from the first portion 24 of the inner surface 16 and a plurality of second bosses 46, 48, 50, 52, 54, 56, 58, 60 project from the second portion 28 of the inner surface 16. The layer of polyurethane elastomer 18 preferably encircles at least one of the first and second bosses. The various first and second bosses can be disposed in the housing 14 to connect the first and second housing shells 24, 26 together, to connect the motor 12 with one or both of the first and second housing shells 24, 26, and/or to connect support structures within the housing 14 such as the motor 12 (as done by the boss 48) or a trigger assembly 62 for engaging the motor 12. Hence, in one embodiment, the layer of polyurethane elastomer 18 can be wedged between the motor 12 and the inner surface 16 of the housing 14.

In the first exemplary embodiment of the invention, the layer of polyurethane elastomer 18 is disposed on both of the first portion or half 24 of the inner surface 16 and the second portion or half 28 of the inner surface 16, including encircling all of the first and second bosses. The layer of polyurethane elastomer 18 includes a first surface (not visible) attached to the inner surface 16 and a second surface 64 opposite the first surface projecting into the cavity. In other words, the second surface 64 of the elastomer 18 is spaced from both the inner surface 16 and the motor 12, exposed within the housing 14. The layer of polyurethane elastomer 18 can dampen vibration generated by the motor 12 during operation without being in direct contact with the motor 12.

The layer of polyurethane elastomer 18 of the various embodiments of the invention is preferably a layer of microcellular polyurethane. Cellasto® is a microcellular polyurethane that can be used to practice the invention. Cellasto® is acquired from the BASF, The Chemical Company. Cellasto® does not measurably capture heat within the housing 14 such that an operational temperature of the power tool does not increase when the elastomer 18 is disposed therein. Hence, although the Cellasto® preferably covers the entire inner surface 16 of the housing 14, the motor 14 will not overheat under normal operating conditions.

Referring now to FIG. 2, in a second exemplary embodiment of the invention, a power tool assembly 10 a includes a motor 12 a. The second exemplary power tool assembly 10 a is a reciprocating saw and includes a tool member 20 a coupled to the motor 12 a and driven in motion by the motor 12 a. The second exemplary tool member 20 a is a saw. The power tool assembly 10 a also includes a housing 14 a having an inner surface 16 a defining a cavity enclosing the motor 12 a. The power tool assembly 10 a also includes a layer of polyurethane elastomer 18 a disposed at least partially on the inner surface 16 a. The polyurethane elastomer 18 a dampens vibration of the motor 12 a during operation of the power tool assembly 10 a. Preferably, in this embodiment, the layer of polyurethane elastomer 18 a is discontinuous. For example, the layer of polyurethane elastomer 18 a includes a plurality of discrete pieces 66 a, 68 a, 70 a, 72 a spaced from one another about the inner surface 16 a. The discrete pieces 66 a, 68 a, 70 a, 72 a of the second exemplary embodiment of the invention are disposed on the handle portion of the power tool assembly 10 a and can have varied thicknesses.

Referring now to FIG. 3, in a third exemplary embodiment of the invention, a power tool assembly 10 b includes a motor 12 b. The third exemplary power tool assembly 10 b is a blower and includes a tool member coupled to the motor 12 b driven in motion by the motor 12 b. The third exemplary tool member 20 b is a fan (not visible). The power tool assembly 10 b also includes a housing 14 b having an inner surface 16 b defining a cavity enclosing the motor 12 b. The power tool assembly 10 b also includes a layer of polyurethane elastomer 18 b disposed on the inner surface 16 b. The polyurethane elastomer 18 b dampens vibration of the motor 12 b during operation of the power tool assembly 10 b.

The housing 14 b includes a first housing shell 22 b defining a first portion 74 b of the inner surface 16 b. The first portion 74 b is less than half of the inner surface 16 b. The housing 14 b also includes a second housing shell 26 b connectable to the first housing shell 22 b to form the housing 14 b. The second housing shell 26 b defines a second portion 76 b of the inner surface 16 b, greater than half of the inner surface 16 b. A first plurality of bosses 30 b, 32 b, 34 b projects from the first portion 74 b of the inner surface 16 b and a second plurality of bosses 46 b, 48 b, 50 b projects from the second portion 76 b of the inner surface 16 b.

A first fastener 78 b extends at least partially through the boss 30 b of the first plurality of bosses and at least partially through the boss 46 b of the second layer of bosses to connect the first housing shell 22 b with the second housing shell 26 b. A first piece 66 b of the layer of polyurethane elastomer 18 b encircles the boss 30 b and a second piece 68 b of the layer of polyurethane elastomer 18 b encircles the boss 46 b.

A second fastener 80 b extends at least partially through the boss 34 b of the first plurality of bosses and at least partially through the boss 50 b of the second layer of bosses to connect the first housing shell 22 b and the second housing shell 26 b with the motor 12 b. A third piece 70 b of the layer of polyurethane elastomer 18 b encircles the boss 34 b and a second piece 72 b of the layer of polyurethane elastomer 18 b encircles the boss 50 b. The third and fourth pieces 70 b, 72 b of the layer of polyurethane elastomer 18 b are compressed between the motor 12 b and the inner surface 16 b of the housing 14 b.

The invention has been described in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. As is now apparent to those skilled in the art, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for convenience and are not to be in any way limiting, the invention may be practiced otherwise than as specifically described. 

1. A power tool assembly comprising: a housing having an inner surface defining a cavity; a motor disposed within said cavity of said housing and coupled to said inner surface; and a layer of polyurethane elastomer disposed at least partially on said inner surface for dampening vibration of said motor during operation of the power tool assembly.
 2. A power tool assembly as set forth in claim 1 wherein said layer of polyurethane elastomer is further defined as a layer of microcellular polyurethane.
 3. A power tool assembly as set forth in claim 1 wherein said layer of polyurethane elastomer includes a first surface attached to said inner surface and a second surface opposite the first surface projecting into said cavity.
 4. A power tool assembly as set forth in claim 3 wherein said second surface of said elastomer is further defined as being spaced from said inner surface and said motor.
 5. A power tool assembly as set forth in claim 1 wherein said layer of polyurethane elastomer covers substantially all of said inner surface of said housing.
 6. A power tool assembly as set forth in claim 6 wherein said housing further including: a first housing shell defining a first portion of said inner surface; and a second housing shell defining a second portion of said inner surface with said second housing shell being connectable to said first housing shell to define said cavity and said layer of polyurethane elastomer disposed on both of said first and said portions.
 7. A power tool assembly as set forth in claim I wherein said housing further including: a first housing shell defining a first portion of said inner surface and having a plurality of first bosses projecting from said first portion of said inner surface; a second housing shell defining a second portion of said inner surface and having a plurality of second bosses projecting from said second portion of said inner surface with said second housing shell being connectable to said first housing shell to define said cavity and said layer of polyurethane elastomer encircling at least one of said first and said second bosses.
 8. A power tool assembly as set forth in claim 7 wherein said layer of polyurethane elastomer encircles all of said first and second bosses.
 9. A power tool assembly as set forth in claim 1 wherein said layer of polyurethane elastomer is discontinuous.
 10. A power tool assembly as set forth in claim 9 wherein said layer of polyurethane elastomer is further defined as a plurality of discrete pieces spaced from one another about said inner surface.
 11. A power tool assembly as set forth in claim 1 further including a tool member coupled to said motor and driven in motion by said motor with said tool member selected from a group consisting of a drill bit chuck, a saw blade and a fan.
 12. A method of assembling a power tool assembly having a housing with an inner surface, a motor, and a layer of polyurethane elastomer, said method comprising the steps of: disposing the layer of polyurethane elastomer on the inner surface; and enclosing the motor within the inner surface of the housing wherein the layer of polyurethane elastomer dampens vibration generated by the motor during operation of the power tool assembly.
 13. A method as set forth in claim 12 wherein the layer of polyurethane elastomer includes a first surface and a second surface opposite the first surface and wherein the step of disposing the layer of polyurethane elastomer is further defined as: attaching the first surface of the elastomer to the inner surface of the housing; and exposing the second surface of the elastomer to an interior cavity of the housing.
 14. A method as set forth in claim 12 wherein the step of disposing the layer of polyurethane elastomer is further defined as substantially covering all of the inner surface of the housing with the layer of polyurethane elastomer.
 15. A method as set forth in claim 12 wherein the step of disposing the layer of polyurethane elastomer is further defined as wedging the layer of polyurethane elastomer between the motor and the inner surface of the housing.
 16. A method as set forth in claim 12 the step of disposing the layer of polyurethane elastomer is further defined as adhering the layer of polyurethane elastomer to the inner surface with an adhesive.
 17. A method as set forth in claim 12 wherein the step of disposing the layer of polyurethane elastomer is further defined as overmolding the layer of polyurethane elastomer on the inner surface. 